全文获取类型
收费全文 | 385篇 |
免费 | 41篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 35篇 |
大气科学 | 28篇 |
地球物理 | 183篇 |
地质学 | 83篇 |
海洋学 | 48篇 |
天文学 | 4篇 |
综合类 | 19篇 |
自然地理 | 36篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 22篇 |
2019年 | 25篇 |
2018年 | 13篇 |
2017年 | 16篇 |
2016年 | 10篇 |
2015年 | 12篇 |
2014年 | 16篇 |
2013年 | 20篇 |
2012年 | 19篇 |
2011年 | 21篇 |
2010年 | 15篇 |
2009年 | 30篇 |
2008年 | 26篇 |
2007年 | 21篇 |
2006年 | 24篇 |
2005年 | 24篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有436条查询结果,搜索用时 15 毫秒
431.
Iraklis Giannakis Panagiotis Tsourlos Costas Papazachos George Vargemezis Antonios Giannopoulos Nikos Papadopoulos Fabio Tosti Amir Alani 《Geophysical Prospecting》2019,67(7):1948-1964
Self-potential is a passive geophysical method that can be applied in a straightforward manner with minimum requirements in the field. Nonetheless, interpretation of self-potential data is particularly challenging due to the inherited non-uniqueness present in all potential methods. Incorporating information regarding the target of interest can facilitate interpretation and increase the reliability of the final output. In the current paper, a novel method for detecting multiple sheet-like targets is presented. A numerical framework is initially described that simulates sheet-like bodies in an arbitrary 2D resistivity distribution. A scattered field formulation based on finite differences is employed that allows the edges of the sheet to be independent of the grid geometry. A novel analytical solution for two-layered models is derived and subsequently used to validate the accuracy of the proposed numerical scheme. Lastly, a hybrid optimization is proposed that couples linear least-squares with particle-swarm optimization in order to effectively locate the edges of multiple sheet-like bodies. Through numerical and real data, it is proven that the hybrid optimization overcomes local minimal that occurs in complex resistivity distributions and converges substantially faster compared to traditional particle-swarm optimization. 相似文献
432.
空间信息移动用户应用服务系统中的GIS关键技术介绍 总被引:3,自引:0,他引:3
探讨了空间信息移动用户应用服务的产生背景。提出一种基于MAS体系结构的整体解决方案.并探讨了在实现该方案过程中研究的GIS技术与方法,并对空间信息移动用户的服务对GIS发展的影响及趋势进行了展望。在基于MAS体系结构的空间信息移动用户整体解决方案中,从技术产生背景出发,重点介绍了空间信息智能体个体结构与组成,MAS协同服务等理论、方法,并简单阐述了空间信息智能体管理、维护与更新的想法。文章中对GIS关键技术的研究与实现从海量空间信息的检索与智能提取;异种GIS平台间互操作理论、算法、技术、原型;面向2.5G以上通用移动设备(GPRS/CDMA)开发GIS Wap Service;基于SMPP与CMPP通信模块,GSM通用移动用户的语音/短消息上下行;基于Spatial—Info Agent与MAS体系的开放式空间信息服务系统技术集成等5个方面进行了介绍。 相似文献
433.
Daniel Trad 《Geophysical Prospecting》2020,68(3):802-814
Least squares migration uses the assumption that, if we have an operator that can create data from a reflectivity function, the optimal image will predict the actual recorded data with minimum square error. For this assumption to be true, it is also required that: (a) the prediction operator must be error-free, (b) model elements not seen by the operator should be constrained by other means and (c) data weakly predicted by the operator should make limited contribution to the solution. Under these conditions, least squares migration has the advantage over simple migration of being able to remove interference between different model components. Least squares migration does that by de-convolving or inverting the so-called Hessian operator. The Hessian is the cascade of forward modelling and migration; for each image point, it computes the effects of interference from other image points (point-spread function) given the actual recording geometry and the subsurface velocity model. Because the Hessian contains illumination information (along its diagonal), and information about the model cross-correlation produced by non-orthogonality of basis functions, its inversion produces illumination compensation and increases resolution. In addition, sampling deficiencies in the recording geometry map to the Hessian (both diagonal and non-diagonal elements), so least squares migration has the potential to remove sampling artefacts as well. These (illumination compensation, resolution and mitigating recording deficiencies) are the three main goals of least squares migration, although the first one can be achieved by cheaper techniques. To invert the Hessian, least squares migration relies on the residual errors during iterations. Iterative algorithms, like conjugate gradient and others, use the residuals to calculate the direction and amplitudes (gradient and step size) of the necessary corrections to the reflectivity function or model. Failure of conditions (a), (b) or (c) leads the inversion to calculate incorrect model updates, which translate to noise in the final image. In this paper, we will discuss these conditions for Kirchhoff migration and reverse time migration. 相似文献
434.
Reverse time migration of multiples can be used to construct subsurface structures where primaries cannot illuminate well. However, the images generated using multiples suffer from severe artefacts due to the cross-talks created by interference among unrelated multiples. We developed a migration approach using water-bottom-related multiples to reduce these cross-talk artefacts. This approach first isolates primaries from the original data and predicts water-column primaries. The nth-order water-column multiples can be obtained by auto-convolving the water-column primaries n times, followed by convolving the nth-order water-column multiples with the primaries to extract the (n+1)th-order water-bottom-related multiples. The approach takes the nth-order water-column multiples as the secondary source and regards the (n+1)th-order water-bottom-related multiples as the receiver wavefield, followed by a cross-correlation imaging condition. Numerical examples from synthetic and field data sets reveal that our approach can provide images with substantially fewer cross-talk artefacts than conventional reverse time migration using multiples, as well as greatly improving shallow imaging compared with reverse time migration of primaries. 相似文献
435.
Elizangela S. Amaral Mota Walter E. Medeiros Roberto G. Oliveira 《Geophysical Prospecting》2020,68(7):2271-2291
Severe limitations of the standard Euler deconvolution to outline source shapes have been pointed out. However, Euler deconvolution has been widely employed on field data to outline interfaces, as faults and thrust zones. We investigate the limitations of the 3D Euler deconvolution–derived estimates of source dip and volume with the use of reduced-to-the-pole synthetic and field anomalies. The synthetic anomalies are generated by two types of source bodies: (1) uniformly magnetized prisms, presenting either smooth or rough interfaces, and (2) bodies presenting smooth delimiting interfaces but strong internal variation of magnetization intensity. The dip of the first type of body might be estimated from the Euler deconvolution solution cluster if the ratio between the depth to the top and vertical extent is relatively high (>1/4). For the second type of body, besides dip, the source volume can be approximately delimited from the solution cluster envelope, regardless of the referred ratio. We apply Euler deconvolution to two field anomalies which are caused by a curved-shape thrust zone and by a banded iron formation. These anomalies are chosen because they share characteristics with the two types of synthetic bodies. For the thrust zone, the obtained Euler deconvolution solutions show spatial distribution allowing to estimate a source dip that is consistent with the surface geology data, even if the above-mentioned ratio is much less than 1/4. Thus, there are other factors, such as a heterogeneous magnetization, which might be controlling the vertical spreading of the Euler deconvolution solutions in the thrust zone. On the other hand, for the iron-ore formation, the solution cluster spreads out occupying a volume, in accordance with the results obtained with the synthetic sources having internal variation of magnetization intensity. As conclusion, although Euler deconvolution–derived solutions cannot offer accurate estimates of source shapes, they might provide a sufficient degree of reliability in the initial estimates of the source dip and volume, which may be useful in a later phase of more accurate modelling. 相似文献
436.
基于对象诊断的空间检验方法(MODE) 总被引:2,自引:0,他引:2
基于对象诊断的空间检验方法 MODE(Method for Object-Based Diagnostic Evaluation),通过在空间场中识别对象,计算对象的相似度,并最终形成两个场的综合相似度来实现对两个空间场的检验。相对于传统的点对点的检验方法,该方法综合考虑了空间位置、形状、面积等多种因素,并通过符合主观判断的模糊逻辑算法计算相似度,克服了数值预报传统检验方法对于空间位置的过度依赖以及TS评分中的"双重惩罚"等不足。个例研究表明该方法具有明显的优势,有较高的实际应用价值。 相似文献